text: //===- llvm/ADT/DenseMapInfo.h - Type traits for DenseMap -------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines DenseMapInfo traits for DenseMap.
  //
  //===----------------------------------------------------------------------===//
  
  // Taken from llvmCore-3425.0.31.
  
  #ifndef LLVM_ADT_DENSEMAPINFO_H
  #define LLVM_ADT_DENSEMAPINFO_H
  
  #include "objc-private.h"
  #include "llvm-type_traits.h"
  
  namespace objc {
  
  template<typename T>
  struct DenseMapInfo {
    //static inline T getEmptyKey();
    //static inline T getTombstoneKey();
    //static unsigned getHashValue(const T &Val);
    //static bool isEqual(const T &LHS, const T &RHS);
  };
  
  // Provide DenseMapInfo for all pointers.
  template<typename T>
  struct DenseMapInfo<T*> {
    static inline T* getEmptyKey() {
      uintptr_t Val = static_cast<uintptr_t>(-1);
      return reinterpret_cast<T*>(Val);
    }
    static inline T* getTombstoneKey() {
      uintptr_t Val = static_cast<uintptr_t>(-2);
      return reinterpret_cast<T*>(Val);
    }
    static unsigned getHashValue(const T *PtrVal) {
        return ptr_hash((uintptr_t)PtrVal);
    }
    static bool isEqual(const T *LHS, const T *RHS) { return LHS == RHS; }
  };
  
  // Provide DenseMapInfo for disguised pointers.
  template<typename T>
  struct DenseMapInfo<DisguisedPtr<T>> {
    static inline DisguisedPtr<T> getEmptyKey() {
      return DisguisedPtr<T>((T*)(uintptr_t)-1);
    }
    static inline DisguisedPtr<T> getTombstoneKey() {
      return DisguisedPtr<T>((T*)(uintptr_t)-2);
    }
    static unsigned getHashValue(const T *PtrVal) {
        return ptr_hash((uintptr_t)PtrVal);
    }
    static bool isEqual(const DisguisedPtr<T> &LHS, const DisguisedPtr<T> &RHS) {
        return LHS == RHS; 
    }
  };
  
  // Provide DenseMapInfo for cstrings.
  template<> struct DenseMapInfo<const char*> {
    static inline const char* getEmptyKey() { 
      return reinterpret_cast<const char *>((intptr_t)-1); 
    }
    static inline const char* getTombstoneKey() { 
      return reinterpret_cast<const char *>((intptr_t)-2); 
    }
    static unsigned getHashValue(const char* const &Val) { 
      return _objc_strhash(Val); 
    }
    static bool isEqual(const char* const &LHS, const char* const &RHS) {
      if (LHS == RHS) {
        return true;
      }
      if (LHS == getEmptyKey() || RHS == getEmptyKey()) {
        return false;
      }
      if (LHS == getTombstoneKey() || RHS == getTombstoneKey()) {
        return false;
      }
      return 0 == strcmp(LHS, RHS);
    }
  };
  
  // Provide DenseMapInfo for chars.
  template<> struct DenseMapInfo<char> {
    static inline char getEmptyKey() { return ~0; }
    static inline char getTombstoneKey() { return ~0 - 1; }
    static unsigned getHashValue(const char& Val) { return Val * 37U; }
    static bool isEqual(const char &LHS, const char &RHS) {
      return LHS == RHS;
    }
  };
    
  // Provide DenseMapInfo for unsigned ints.
  template<> struct DenseMapInfo<unsigned> {
    static inline unsigned getEmptyKey() { return ~0U; }
    static inline unsigned getTombstoneKey() { return ~0U - 1; }
    static unsigned getHashValue(const unsigned& Val) { return Val * 37U; }
    static bool isEqual(const unsigned& LHS, const unsigned& RHS) {
      return LHS == RHS;
    }
  };
  
  // Provide DenseMapInfo for unsigned longs.
  template<> struct DenseMapInfo<unsigned long> {
    static inline unsigned long getEmptyKey() { return ~0UL; }
    static inline unsigned long getTombstoneKey() { return ~0UL - 1L; }
    static unsigned getHashValue(const unsigned long& Val) {
      return (unsigned)(Val * 37UL);
    }
    static bool isEqual(const unsigned long& LHS, const unsigned long& RHS) {
      return LHS == RHS;
    }
  };
  
  // Provide DenseMapInfo for unsigned long longs.
  template<> struct DenseMapInfo<unsigned long long> {
    static inline unsigned long long getEmptyKey() { return ~0ULL; }
    static inline unsigned long long getTombstoneKey() { return ~0ULL - 1ULL; }
    static unsigned getHashValue(const unsigned long long& Val) {
      return (unsigned)(Val * 37ULL);
    }
    static bool isEqual(const unsigned long long& LHS,
                        const unsigned long long& RHS) {
      return LHS == RHS;
    }
  };
  
  // Provide DenseMapInfo for ints.
  template<> struct DenseMapInfo<int> {
    static inline int getEmptyKey() { return 0x7fffffff; }
    static inline int getTombstoneKey() { return -0x7fffffff - 1; }
    static unsigned getHashValue(const int& Val) { return (unsigned)(Val * 37U); }
    static bool isEqual(const int& LHS, const int& RHS) {
      return LHS == RHS;
    }
  };
  
  // Provide DenseMapInfo for longs.
  template<> struct DenseMapInfo<long> {
    static inline long getEmptyKey() {
      return (1UL << (sizeof(long) * 8 - 1)) - 1UL;
    }
    static inline long getTombstoneKey() { return getEmptyKey() - 1L; }
    static unsigned getHashValue(const long& Val) {
      return (unsigned)(Val * 37UL);
    }
    static bool isEqual(const long& LHS, const long& RHS) {
      return LHS == RHS;
    }
  };
  
  // Provide DenseMapInfo for long longs.
  template<> struct DenseMapInfo<long long> {
    static inline long long getEmptyKey() { return 0x7fffffffffffffffLL; }
    static inline long long getTombstoneKey() { return -0x7fffffffffffffffLL-1; }
    static unsigned getHashValue(const long long& Val) {
      return (unsigned)(Val * 37ULL);
    }
    static bool isEqual(const long long& LHS,
                        const long long& RHS) {
      return LHS == RHS;
    }
  };
  
  // Provide DenseMapInfo for all pairs whose members have info.
  template<typename T, typename U>
  struct DenseMapInfo<std::pair<T, U> > {
    typedef std::pair<T, U> Pair;
    typedef DenseMapInfo<T> FirstInfo;
    typedef DenseMapInfo<U> SecondInfo;
  
    static inline Pair getEmptyKey() {
      return std::make_pair(FirstInfo::getEmptyKey(),
                            SecondInfo::getEmptyKey());
    }
    static inline Pair getTombstoneKey() {
      return std::make_pair(FirstInfo::getTombstoneKey(),
                            SecondInfo::getTombstoneKey());
    }
    static unsigned getHashValue(const Pair& PairVal) {
      uint64_t key = (uint64_t)FirstInfo::getHashValue(PairVal.first) << 32
            | (uint64_t)SecondInfo::getHashValue(PairVal.second);
      key += ~(key << 32);
      key ^= (key >> 22);
      key += ~(key << 13);
      key ^= (key >> 8);
      key += (key << 3);
      key ^= (key >> 15);
      key += ~(key << 27);
      key ^= (key >> 31);
      return (unsigned)key;
    }
    static bool isEqual(const Pair &LHS, const Pair &RHS) {
      return FirstInfo::isEqual(LHS.first, RHS.first) &&
             SecondInfo::isEqual(LHS.second, RHS.second);
    }
  };
  
  template<typename T>
  struct DenseMapValueInfo {
      static inline bool isPurgeable(const T &value) {
          return false;
      }
  };
  
  } // end namespace objc
  
  #endif
  